Author:

Most formulations of spin density functional theory (SDFT)
restrict the
magnetization vector field to have global collinearity. Nevertheless,
there exists a wealth of strong non-collinearity in nature, for
example
molecular magnets, spin-spirals, spin-glasses and all magnets at
finite
temperatures.
The local spin density approximation (LSDA) can be extended to
these non-collinear cases [1] but this extension has the
undesirable
property of having the exchange-correlation (xc) field parallel
to the
magnetization density at each point in space. When used in
conjunction
with the equation of motion for the spin magnetization
in the absence of spin currents and external fields [2,3],
this local
collinearity eliminates the torsional term, resulting in
no time evolution. This severe shortcoming of LSDA, where the
physical
prediction is qualitatively wrong, opens up an important new
direction for
the development of functionals where this time evolution is correctly
described.
Towards this goal, I will describe our extension of the Kohn-Sham
optimized effective potential (OEP) method to the non-collinear
case and
derive the corresponding integral equations, applicable to both
finite and
extended systems [3,4]. Most importantly I'll show that the
resulting
magnetization and xc field are not locally collinear to each
other for
real solids, and will therefore produce manifestly different
spin-dynamics.
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[1] J.~Kuebler, K.-H.~Hoeck, J.~Sticht and A.~R.~Williams,
J.~Phys.~F{\bf 18}, 469 (1993).
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[2] K.~Capelle, G.~Vignale and B.~L.~Gyoerffy,
Phys.~Rev.~Lett.{\bf 87}, 206403 (2001).
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[3] S.~Sharma, J.~K.~Dewhurst, C.~Ambrosch-Draxl, S.~Kurth,
N.~Helbig, S.~Pittalis, S.~Shallcross, L.~Nordstroem and
E.K.U.~Gross Phys.~Rev.~Lett.{\bf 98}, 196405 (2007)
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S.~Sharma, S.~Pittalis, S.~Kurth, S.~Shallcross, J.~K.~Dewhurst
and E.K.U.~Gross Phys.~Rev.~B{\bf 76}, 100401 (Rapid Comm.) (2007)

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2008.MAR.S5.5